What is a family preference category? Qualified relatives of a U.S. citizen or permanent resident who are not known as an immediate relative may have to wait for a visa to become available before they can apply for permanent residency. These categories are known as Preference Categories and include:
Sedimentary rocks are formed by sediment that is deposited over time, usually as layers at the bottom of lakes and oceans. This sediment can include minerals, small pieces of plants and other organic matter. The sediment is compressed over a long period of time before consolidating into solid layers of rock. Sedimentary rocks forms layers called strata which can often be seen in exposed cliffs.
Sedimentary rocks are called secondary, because they are often the result of the accumulation of small pieces broken off of pre-existing rocks. There are three main types of sedimentary rocks: Clastic: your basic sedimentary rock.